Field of the Invention
The present invention relates generally to valves for controlling fluid flow. More particularly, the invention concerns valves for use in the controllable release of entrapped body fluids.
Discussion of the Prior Art
In certain instances the human body fails to properly drain fluid from its cavities. For example, in an ailment known as hydrocephalus, cerebrospinal fluid is not properly drained from the brain. As a consequence, the patient may suffer an abnormal expansion of the cerebral ventricles, an enlargement of the skull and, if the condition is not corrected, atrophy of the brain. One of the most successful devices developed in the past for draining fluids from body cavities is described in U.S. Pat. No. 4,364,395 issued to one of the present co-inventors. U.S. Pat. No. 3,111,125 issued to Schulte and U.S. Pat. No. 3,595,240 issued to Mishler describe other prior art drainage apparatus. The devices disclosed in the Schulte patent comprise a combined pump and check valve. The device is disposed between a drainage catheter which is inserted into the cranium and a shunt tube with a check valve which generally discharges into the heart.
Drawbacks of many of the prior art drainage devices include clogging, valve degredation and failure as a function of time. Additionally, many of the prior art devices are bulky, difficult to surgically emplace and fail to properly control the amount of fluid drained from the body cavity. In this latter regard, it has been postulated that ideally the drainage device should precisely sense the fluid pressure generated in the body cavity to be drained and permit drainage to occur only when the fluid pressure in the body cavity reaches a predetermined level.
The apparatus of the present invention overcomes the drawbacks of the prior art devices by providing a device which is compact, highly reliable in operation and one which remains closed until a predetermined pressure in the body cavity to be drained is reached. Further, in one embodiment of the fluid flow control valve of the present invention, the valve assembly can be "tuned" to a desired opening pressure as a final assembly step. Additionally, as will be better understood from the discussion which follows, combining two of the valve assemblies of the basic fluid flow control device of the invention in series with an elastomeric section therebetween permits the apparatus to be used to actively pump fluid downstream by squeezing the central connecting section.